Method of making lenses or the like



' July 30, 1929. CHQMSTQCK 1,722,368

OD OF MAKING LENSES OR THE LIKE Original Filed May 23, 1922 2 Sheets-Sheet 1 y 1929- D. F. COMSTOCK 1,722,368

METHOD OF MAKING LENSES OR THE LIKE Origihal Filed Ma 23. 1922 2 Sheets-Sheet 2 Merck? zielliiomajlaak Patent Jul so, ieza.

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DANIEL F. COMSTOCK, OF BROOKLINE, MASSACH'O'SETTS, ASSIGNOB TO' COMSTOCK & WESCOTT, INQ, OF BOSTON, MASSACHUSETTS, A CORPORATION OF MASSACHUSETTS.

METHOD OF MAKING LENSES OR THE LIKE.

Original application filed May 23, 1922, Serial No. 562,989. Divided and this application filed August 1, 1927. Serial No. 209,696. a

This invention relates particularly to headlight screens or lenses of the type adapted to be mounted in the front opening of a headlight for the purpose of spreading the light,

bending it downwardly, or otherwise controlling the distribution properly to illuminate the field and minimize the glaring effect. However, it will be evident that, in its broader aspect, the invention compre'hends lenses or refractors adapted for various uses. 1 Objects of the invention are to provide a screen or lens"'whic lr is light'in weight and relatively thin and which can be packed and shipped in less space and with less danger v of breakage than the ordinary all-glass lens. Another object is to provide ascreen in which the lens formation does not comprise such wide dilferences in thickness as to involve deep grooves or depressions and high ridges or protuberances. Further objects are to provide a method of manufacture which is rapid and inexpensive, which requires a relatively small machine equipment, which results'in an unusually small percentage of imperfect lenses, and which affords a wide latitude'of variation in the shape and arrangement of the refractors with little additional equipment. In one aspect the present invention relates to a light-transmissive plate of glass or other suitable material and a relatively soft coating of light-transmissive material, such as gelatin or other collodial substance, the coating having parallel refractive sections adapted to alter the directional characteristics of the light passing therethrough. In the case of a light-spreading screen, the refractive sections may be in the form of cylindrical lenses, that is, generally cylindrical in contour although not necessarily exactly cylindrical, and either 4.0 concave or convex or alternately concave and convex in the general form of a sinusoidal curve; an essential characteristic residing in the parallel arrangement of the refractors,

that is, generally parallel and not necessarily exactly parallel, whereby the light is bent or spread predominantly in one dimension. In

the case of a screen for downwardly bending the light to ayoid glaring efiects the lens formatiommay be in the form of a series of sections having inclined boundaries or prismatic surfaces. v

Certain of the objects of the invention are attained by making the refractors of small cross-sectional dimensions, e. g. of the order of a few hundredths of an inch wide and a few thousandths of an inch thick, these small dimensions being made possible by the method of manufacture constituting a part of this invention.

In. another aspect the invention relates to a lens or screen comprising a series of lightindurated colloid refractors, preferably integrally connected together and preferably supported on a light-transmissive plate as aforesaid.

The method of making the aforesaid lens or screen comprises exposing a light sensitive layer of light-transmissive material in varying degree throughout its area depending upon the lens formation desired, and sub sequently treating the exposed and unexposed portions of the layer selectively to develop the lens formation. For example, with the light-sensitive layer inthe form of a coating on a glass or other plate, it-is possible so to treat the layer that, as a result of the action of light, the outer portion of the light-sensitive layer may be dissolved ofl' leaving the portion next to the plate in relief. Either the exposed or theunexposed portions of the layer may be dissolved (iii, the layerbeing exposed through the plate if the unexposed portion is to be etched 0E and from the opposite side if the exposed portion is to be removed, whereby the remaining portion is left adhering to the plate. One simple and efiective way of efiecting the selective removal of a part ofthe light-sensitive layer is to form the light-sensitive layer of bichromated gelatin wherein the exposed portions are hardened directly by light (in contradistinction to a photographic emulsion in which the exposed portions do not harden or otherwise become selectively separable from the: unexposed portions until after development or other intermediate treatment) ,then to expose. the layer through the plate, and subsequently to dissolveofi the soft unexposed portions.

In order to ,illustrate the invention 1 have shown certain concrete embodiments thereof in the accompanying drawings, in which:

, Fig. 1 is a rear viev of a headlight screen;

Fig. 2 is a section of a portion of the lens on an enlarged scale;

I glass plate.

Figs. 3 and 4 illustrate two typical lens difference between the thicker and thinner formations on still further enlarged scale; portions of the lens formation for a glven Fig. 5 illustrates one method of exposing exposure. L the light-sensitive layer; The method of expos ngthe light-sensltlve Fig. 6 is a face view of a portion of a grid ayer Illustrated 1n F g. 5 where P is the ada ted .t b l y d as ill t t d in glass plate and C the light-sensitive coating, 5;

Fig. 7 is a face view of a portion of a grid l l typ 0f g rld Il r d in g and or screen somewhat different from that shown 6 mprises a glass plate having on one face i Fi 6;v thereof a series of opaque lines A separated Fig. 8 is a sectional view of still a different y nsparent lines B which may have the typ of g id or screen; d 1 same wldth as the opaque lIHQS As shown Fig. 9 illustrates a screen or shutter for 111 F g- 5, th grid 1s placed behlnd the glass use in exposing the light-sensitive layer of Plate P Wlth the hlled slete eohtaetlhg Wlth the lens or for use in making a grid such as t glee? Plate and the hght'sehsltlve coat illu t at d i Fi 8 mg C is exposed through the grid and The particular embodiment of the inven' h e gh the pl tion illustrated in Figs. 1 and'2 comprises l g the dlstfmee from h hght a glass plate P having upon one face thereof, t g h Wldth the 111188 011 he g preferably the rear face, a series of parallel the dlmehsloh'of the hg Source ransversely vertical lenses L which have such cross-secf e e of h E the hghtsehsl tional contour as to produce the desired light l coat/111g y be exposed dePth distribution. As above stated these lenses hounded y t q y currvlhg h 'h may be either convex as shown at- L in Fig. 4 1S gehel'ahy slhhseldal h Shape lhthcated or concave or alternately concave and cont t diffraction effect of the gnd as Shown t L" i Fi 3 Th lenses tributing to the smoothness of the: curve. are preferably of the order of a few hun- F mp e, PP Such as lndlcated dredths of an inch wide, for example two y the hhe D 111 5 ey he P d or three hundredths of an inch, and a few by a e y Vapor t p. epe Parallel thousandths of an inch thick, for example to the hhes of h grld pl f i y tour four thousandths of an inch, thus adding feet e the g and havlhg a hght h only a slight additional thickness to the lens eRproxhhately hr r of lheh or screen over and above the thickness of the the glass p e P belhg approxlmately one-eighth of an inch thick and the opaque A suitable light-sensitive coating in which and thenspal'eht lines hands of the grid the lenses or refracting elements are to be each being approximately twenty-five thou 'may then be appliedto the glass plate or sequently employed and to produce the parformed comprises bichromated'gelatin which Sahdths of an h Wldemay be prepared and applied as follows: he e shthel'ehtly long Dissolve 4 grams of ammonium bichromate 9 the hhe D to the Outer in 14 c. c. of 'water, the bichromate dissolv- 111g ing at approximately 130 F. Dissolve 14 grams of gelatin in 98 c. c. of water, the gelap q e t ahspareht seetlehs P as tin being permitted to soak in the water and Shown 111 F y p y l Fh th Water b i warmed t approximately as shown in F g. 7 1n whlch the transmissiv ty 110 F. until a homogenous watery mass reof the g h e y ant-t grattually sults. These two mixtures, the bichromate creases d decreases, 111 one dlmehslohathere solution and the gelatin mass, are then by producing relatively opaque portions A thor u hl mi d, Thi bi d i t and relatively transparent portions B wh1ch gradually merge with each other hrogh portions of intermediate transmissivity. y predetermining the range and rate of varia- The exposure may to carry the crests surface of the coat- C or it may be somewhat shorter.

other-light-transmissive support by placing the support in a horizontal position and pouring the mixture thereupon at a temperature of approximately 110 F, t a d th f one d mension a lens formation of any deproximately one-eighth of an inch. The ired depth and shape may be produced.

mixture spreads uniformly over the surface ig- 8 illu aIlOthGI fQ m f grid 00mof the support and when dry has a thickness prising a glass plate D havmg on one face varied to suit the particularly treatment subdegree along the proportions of the ingredients may be terial adapted to transmit light in varying one dimension corresponding to the variable thickness of the ridges. For example, the ridges E may be formed according to the present invention by exposing a light-sensitive emulsion as above described .or as hereinafter described, subsequently reticular lens formation desired. For example, a decrease in the proportion of bi-- chromate increases the contrast of the subsequent light exposure and consequently the tion of the transmissivity of the grid in the t involves the use of a light grid G. The pari By properly predeter- 1 Instead of using a grid having alternate moving the soft unexposed gelatin, and then staining the remaining gelatin with a dye adapted to absorb the exposing light in proportion to the thickness of the ridges.

Fig. 9 illustrates a screen or shutter compfising a sheet or band of opaque material (a portion of which is shown in black in the figure) having a slot S of variable width extending thereacross, the variation in 'the Width of the slot depending upon the lens formation which it is desired to make. In use the light through this slot is spread over the entire light-sensitive layer in a direction perpendicular to the lengthwise axis of the slot, i. e. vertically in Fig. 9, either by motion of the slot and light-sensitive layer relatively to each other or by using, in connection with a copying lens, a lens dispersive in one direction only. Thus the light sensitive layer is exposed uniformly in the direction perpendicular to the lengthwise axis of the slot but is exposed to a variable depth parallel to the lengthwise axis of the slot. By suitably proportioning the contour of the slot S any desired variation in exposure in a direction parallel to the lengthwise axis of the slot may be obtained, the particular exposure desired. being determined either experimentally or mathematically. Owing to the difficulty of making a slot having dimensions as small as those-of the lens formation to be made, the shutter shown in Fig. 9 is preferably made many times. larger and then employed at a distance from the light-sensitive coating in a lens system adapted to reduce the dimensions to the desired degree, for example to approximately twenty-five thousandths of an inch wide for each lens.

A very satisfactory procedure is to make a screen or grid such as shown in Fig. 8 by means of a shutter such as shown in Fig. 9

and then to employ this grid as illustrated in S of the shutter being differently proportioned in the latter case to produce the desired exposure on the lens.

After, the light sensitive coating has been exposed as described, the outer portion of the coating may be etched ofl by immersion in a suitable bath. Where the light sensitive coating comprising bichromated gelatin water makes a very suitable bath, in which case a particularly good method of bathing comprises soaking the coating in cool water for approximately fifteen minutes and then in water at a temperature of about 120 F. for approximately fifteen minutes, the warm water being agitated during the latter fifteen minutes.

This application is a division of application Serial No. 562,989, filed May 23, 1922.

I claim:

1. The method of making a lens which comprises exposing a light-sensitive layer through a slot of variable width, spreading the light over the layer transversely of the slot to expose the layer in parallelsections, and rendering the layer differentially absorptive in accordance with the variable exposure.

2. The method of making a lens which comprises exposing a light-sensitive layer through a slot of variable width, spreading the light over the layer transversely of the slot to expose the layerin parallel sections with the degree of exposure varying in waves transversely of the sections, etching 0B. the unexposed portions of the layer, and staining the remaining portions.

3. Themethod of making a lens from a light-sensitive coating on a transparent support which comprises exposing the coating through the support in parallel sections with the degree of exposure varying in waves transversely of the sections, and. etchin off the unexposed portions of the coating to form a wavy lens structure,

Signed by me at Boston, Massachusetts,

of Jul 1927. DANI L F. COMSTOCK.

this 26th day 

